Compounds having strong light absorption at specific wavelength are used in recording layers of optical recording media such as CD-R, DVD-R, DVD+R, and blue laser recording discs and in optical elements of image display devices such as liquid crystal displays (LCD), plasma display panels (PDP), electroluminescence displays (ELD), cathode-ray tube displays (CRT), fluorescent display tubes, and field emission displays.
Optical elements in image display devices are used, for example, as light absorbers in color filters. Image display devices generate color images by combining light in three primary colors, red, blue, and green, but the beam used for generating color images includes light lowering display quality such as 550- to 600-nm light, which is between green and red, and also includes 750- to 1100-nm light, which possibly causes malfunction of infrared remote controllers. Optical filters are required to have a function of selectively absorbing light in such unwanted wavelengths and also absorbing light at 480 to 500 nm and 540 to 560 nm in order to prevent reflection and glare of external light from fluorescent lamps or others. In image display devices and the like, therefore, optical filters comprising light-absorbing compounds (light absorbers) selectively absorbing light at such wavelengths are used.
Conventionally, an optical filter has been manufactured by laminating an optical film comprising a light-absorbing compound (light absorber) selectively absorbing light at specific wavelengths with a transparent substrate such as glass via an adhesive layer. Thus, there have been problems of high cost due to many steps involved in production and difficulty in preparing thin layer-shaped optical filters.
Patent Document 1 discloses a film for electronic displays containing a dye and carbon black in the adhesive layer, Patent Document 2 discloses an adhesive containing a dye, and Patent Document 3 discloses a filter for displays using an adhesive comprising a dye.
It was however difficult to prevent the dye compounds in the adhesive layers from photo-, thermal, or other degradation, and there has been no available optical filter to ensure sufficient optical properties yet.
On the other hand, Patent Document 4 discloses a color filter containing a color material in which a dye is intercalated in a clay, Patent Document 5 discloses an aqueous ink composition containing a colored composite wherein interlayer ions in smectite, which is a clay-type intercalation compound, are exchanged with dyes, and Patent Document 6 discloses an optical filter having a filter layer containing fine particles in which a dye is absorbed on surfaces thereof. However, nothing has been suggested on use of such color materials or colored composites in adhesive layers of optical filters or on improvement of moist heat resistance of optical filters by using such color materials or colored composites.
Patent Document 7 discloses a near infrared-absorbing film having a near infrared-absorbing layer containing a cyanine compound having a specific structure and a diimmonium compound as essential components. In the near infrared-absorbing film, however, use of another dye compound such as a cyanine compound together with the diimmonium compound caused deterioration of the moist heat resistance and/or light resistance due to the interaction with such another dye compound, while dispensing with such another dye compound increased absorption in the visible region. Thus, performances of this film were not sufficient.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-82302    Patent Document 2: Japanese Patent Laid-Open Publication No. 2004-107566    Patent Document 3: Japanese Patent No. 3311720    Patent Document 4: Japanese Patent Laid-Open Publication No. H10-77427    Patent Document 5: Japanese Patent Laid-Open Publication No. H10-133013    Patent Document 6: Japanese Patent Laid-Open Publication No. 2000-338325    Patent Document 7: Japanese Patent Laid-Open Publication No. 2003-21715